1. Field of the Invention
The present invention relates to an image forming apparatus using electrophotography, for example, a copying machine or a printer.
2. Description of the Related Art
In inkjet printers, so-called marginless printing is adopted popularly. In marginless printing, a transfer material, such as paper, which does not have a margin on its periphery is used, and an image is formed over the entire transfer material. In LBPs and so on using electrophotography, there is also an increasing demand for marginless printing. For example, Japanese Patent Laid-Open No. 2004-45457 proposes an image forming apparatus capable of marginless printing. In this image forming apparatus, a toner image larger than a transfer material is formed on an image bearing member, and part of the toner image is transferred onto the transfer material, thus achieving marginless printing.
When a toner image on an image bearing member, such as an intermediate transfer member, is transferred onto a transfer material, part of the toner image to be transferred is sometimes scraped off by a leading edge of the transfer material. In this case, the toner image that has been partly scraped off by the leading edge of the transfer material is transferred onto the transfer material. This phenomenon causes defective image forming near the leading edge of the transfer material. Here, defective image forming refers to soiling of the back side of the transfer material with toner, soiling of a leading end face of the transfer material with toner, or density unevenness at the leading edge of the transfer material.
When a margin is formed on the periphery of the transfer material, a toner image is not formed in a region on the image bearing member corresponding to the margin, and therefore, defective image forming rarely occurs.
In contrast, in marginless printing, since a toner image is formed over the entire transfer material, defective image forming occurs quite frequently. Further, although a toner image should be formed to the edges of the transfer material in marginless printing, part of the toner image near the edge is scraped off. Thus, defective image forming is more obvious in marginless printing.